There is a problem with your battery, so your computer might shut down suddenly." The warning is normally issued after using the computer's basic input output system (BIOS) to determine whether a battery needs replacement, but in this case it appears the operating system and not the battery is the problem.

These customers say their PC's battery life is noticeably lower, with some going as far as saying that it has become completely unusable after a few weeks of use.

To make matters worse, others are reporting that downgrading back to an earlier version of Windows won't fix the problem.

The thread has managed to garner some 350 posts over the last eight months, about half of which were posted over the last month or so.

The only official answer was posted and approved by a Microsoft moderator in June: "Windows 7 has had issues identifying certain batteries, as you can easily see searching the forum," wrote Adam M, Microsoft Certified Professional.

"Due to such prevalence, it is safe to say the issue will be addressed. Thank you for reporting your troubles on the forums."

We contacted Microsoft to see if the company had made any headway. "We are investigating this issue in conjunction with our hardware partners," a Microsoft spokesperson told Ars.

"The warning received in Windows 7 uses firmware information to determine if battery replacement is needed. We are working with our partners to determine the root cause and will update with information and guidance as it becomes available."

Brian Ehlert, a Microsoft MVP, posted eight times in the thread, having begun to experience the issue as well. He went from having three hours of battery life on beta and RC builds of Windows 7 to about 20 minutes on Windows 7 RTM (and from eight hours to 15 minutes on another computer).

He also responded to a workaround for disabling Windows 7 from shutting down on battery issues saying that this may result in the operating system shutting down later, but saying that it doesn't fix the root cause of the problem.

Another fix that worked for some, but not for Ehlert, was letting the battery drain completely outside of the operating system so that it is recalibrated.

Ehlert's last response in the thread was that he went out to buy a new battery, though he has yet to report back if this fixed the problem or if the second battery is following the first one to an early grave.

The battery life issue on Windows 7 actually dates back to June 2009, according to the forum thread. At the time, Windows 7 wasn't yet released, but the issue was apparently in both the beta and Release Candidatebuilds.

Apparently the problem wasn't widespread enough for Microsoft's quality control team to fix it in time for the RTM build compiled in July 2009, though some users say they've only started to notice the issue with the RTM build and that beta builds worked just fine.

Nevertheless, there are always a few users who have issues. Microsoft's stance is that the root cause of the issue is related to specific system firmware, meaning it only affects machines with certain BIOS releases.

Judging from the forum thread, however, customers disagree with Microsoft's explanation since the problem appears to affect notebooks from more than just one OEM, and some claim their vendors have informed them that it's a Microsoft problem.

The phrase "class action lawsuit" is mentioned by three different posters so far; users are getting impatient with the software giant as it fails to give a timely official response. Microsoft has sold more than 60 million copies of Windows 7, and it's not clear what fraction of those owners are having problems with battery life.